Resistance thermometer



E. A. DE BRUYNE RESISTANCE THERMOMETER Oct. 7, 1952 3 Sheets-Sheet l Filed July 19, 1947 E. A. DE BRUYNE RESISTANCE THERMOMETER Oct. 7, 1952 3 Sheets-Sheet 2 Filed July 19, 1947 has occurred.

Patented Oct. 7, 1952 UNITED STATES PATENT FFHQE' 2,612,780 r f sssrsrmvos THERMOMETEE Emil A. DeBruyne, Elmwood Park, Ill; assignor to Illinois Testing Laboratories, Inc., Chicago, 111., a corporation of Illinois Application July 19, 1947, Serial No. 762,070

Claims. 1

This invention relates, in general, to the art of measuring temperatures, and has particular relation to an improved resistance thermometer.

'While the particular instrument which I shall describe hereinafter in connection with the drawings is a portable resistance thermometeradapted for'use in testing or measuring temperatures at a plurality of stations or points, for example in different rooms or spaces, inside or outside, or in different cars or trucks-such as 'reirigeratedears or trucks-or cars or trucks for food or other products. andin testing or measuring the operating temperatures of water, oil, air and/or exhaust gases of dieselengines or automotive engines; also for testing or measuring the temperature of any compartment or space where a reading is desired without opening the door or entering such compartment,it is to be understood that the instrument of the present invention isnot limited to such uses but may be employed in all similar work as suitable or desired.

Prior devices of theclass described have usually been provided with an indicator of selected size and desired scale range, a temperature? re.- sponsive element or thermobulb for each point or place of which a temperaturereading is desired, dry batteries to furnish thezoperating cur.- rent, triple wire connections extending from. the

indicator to each temperatureresponsive element, and a selector switch mechanism .for selectively connecting the indicator to the respective temperature responsive elementsyalso a fixed resistance, not temperaturezresponsive, with means for switching this resistance intoand out of cir- =cuit with the indicator for testpurposes as known addition,'be'en large; and heavy. The wiring :has

been complicatedand, irrespective of whether the instrumentisvoi the portable type or the system is fixed, the switches orstation selectors have been 1arge,,,complicated and expensive, andthe provisions such as those men- 1 other features'have presentedlimitations to more widespread ,adoption of such, instruments than One of the main'objectstoflthe present invention is to provide an improved form of portable resistance thermometer in which problems previously presented are overcome.

Another object of the/invention is to provide a portable resistance thermometer having various features of novelty and advantagesand which is particularly characterized by its simplicity in construction, its economy'in manufacture, its light weightand small .size for convenient portability and use,nand its eiiectiveness in use for the intended purposes.

Another object of the invention is the provision of an improved resistance thermometer of the class described which is adapted to indicate accurately all of the various'temperatures which the instrument is adapted to measure.

Another objectof the invention .is the provision of an improved instrument of the class described for measuring temperatures at a plurality of points or station's'without selector switch mechanism or the like for selectively connecting the indicator of the instrument to the various temperature responsiveelements. 7

Another object. of the invention is the provision of an improved instrument of the class described for measuring temperatures at a plurality of points 'orstations without complicated and costly wiring; particularly without triple wire connections'from the indicator to each'of the temperature responsive elements.

" Another object *of'the invention is the provision of an instrument of the class described that maybe employed, 'for example 'for testing or measuring the temperature of any compartment or space where a reading isedesired without opening the door or enteringsuch compartment; also without complicated and expensive temperature measuring installations and instruments for such "compartmentsor'spaces; Further-objects and advantages of the inven- -'sistance thermometer embodying-the present invention, showing thelead conductor and a quick .detachabIeterminaI connection forming a part of the instrument; r r

Figure'Z isan'elevational'view of one form of temperature responsive" element or thermobulb for use w1th the instrument shown in Figure 1,

showing oneform of connector device adapted vfor connectingathe.leadrconductor ofthe temperature responsive' element withthe-lead condoctor of the instrument.;"-

Figure 3 is an end view of the terminalconnec r at the end of the lead conductor shown-in Figure 4 is a fragmentary detail section taken on the line 4-4 of Figure 3;

Figure 5 is an end view of the terminal connector at one end of the handle of the instrument;

Figure 6 is a side elevational View of the instrument shown in Figure 1;

Figure 7 is a rear elevational view of the instrument shown in Figure 1;

Figure 7A is a fragmentary rear elevational view of an instrument similar to Figure 7 showing the resistance measuring circuit within the instrument case and how the different resistance plugs for introducing different resistances for different temperatures are applied.

Figure 8 is a fragmentary longitudinal section through the handle of the instrument on sub stantially the line 8--8 of Figure 7;

Figure 9 is a wiring diagram of a temperature measuring instrument constructed according to the present invention;

Figures 10, 11 and 12 are side elevational views of three different resistance plugs for introducing different resistances for different temperature ranges;

Figure 13 is a wiring diagram of the fixed resistance for standardizing the instrument, showing the same in relation to the wiring diagram shown in Figure 9;

Figure 14 is a fragmentary detail section taken on the line |4-|4 of Figure 8; and

Figure 15 is a circuit diagram of the resistance plugs shown in Figures 10, 11, and 12.

Referring now to the drawing, it will be observed that the reference character I0 designates generally a measuring instrument, preferably of the DArsonval type which is provided with the conventional pointer |I arranged to be operated by a moving coil relative to a scale I2 which is suitably calibrated to indicate temperature, as well known in the art. The instrument II] has a case I3 removably fastened to an insulating base I4 to which is attached a handle l5 to permit holding the instrument by the hand of an, operator, for use as will be presently described, and in position where the scale I2 is readily visible.

On the rear of the base I4 there are provided three terminal posts I6, IT, and I8 which it will be understood are connected to operate the moving coil within case I3 and thereby the pointer II relative to scale I2 when the instrument is connected to the temperature responsive element, or to the fixed resistance element (not temperature responsive), for standardizing the instrument. A flexible lead conductor I9 is secured at one end to the rear of base I4 by a bracket 20. The conductor I9 has triple wires 2|, 22, and 23 connected to the posts I6; I1, and I8 and thereby in circuit with the instrument circuit. The opposite end of conductor l9 has a terminal connector 24 which comprises, for example, a metallic connector shell 25 having limited rotation on a metallic sleeve 26 within which is mounted an insulating plug 21 from the outer end of which project three terminal prongs 28, 29, and 30, one in circuit with each of the wires 2|, 22, and 23.

The handle I5 is formed of metallic material, and positioned end to end in the tubular part of the handle-which is of cylindrical formare a pair of dry batteries 3| and 32 of the flashlight type. The batteries 3| and 32 are clamped by a metallic end cap 33 endwise within the handle I5, with the central electrode 34 of the innermost battery in contact with a terminal contact 35, the

central electrode 36 of the outermost battery in contact with the base of the cylindrical or cupshaped outer electrode 31 of the innermost battery, and the base of the cylindrical or cupshaped outer electrode 38 of the outermost battery in circuit with the end cap 33 through coiled spring 38' as shown. The batteries may, of course, be reversed, in which case the base of the cylindrical or cup-shaped outer electrode of the innermost battery will contact the terminal contact 35, whereas the base of the cylindrical or cup-shaped outer electrode of the outermost battery will contact the central electrode of the innermost battery, and the central electrode of the outermost battery will be in circuit with the end cap 33. A conductor 40 leads from the terminal contact 35 through the upper angular portion of the handle I5 which is attached to the rear of base I4 and into the instrument where it connects the batteries in circuit, as will presently appear.

Removably screwed at 42 into the end cap 33 is a metallic sleeve 43. Fixed within the enlarged outer end of the sleeve 43 is an insulating plug 44 having three openings, shown gen erally at 45, into which the terminal prongs 28, 29, and 30 of the terminal connector 24 are adapted to be inserted, and, when so inserted, contact terminal contacts shown diagrammatically at 4B, 41, and 43 in Figure 13. The cap 33 is screwed at 50 into the adjacent end of the tubular handle I5.

The reference character 5| designates the fixed resistance which is not temperature responsive, and'is adapted for standardizing the instrument. It is shown in Figure 8 carried by an insulating spool 52 and positioned within cap 33 when the connector sleeve 43 is applied thereto. Leads 53, 54 and 55 connect the resistance 5| in circuit with the terminal contacts 46, 41 and 48, the leads 53 and 54 extending from one end of resistance 5| to terminal contacts 46 and 47, respectively, and the lead 55 extending from the opposite end of resistance 5| to terminal contact 48, all as shown diagrammatically in Figure 13.

Referring to Figure 9, the measuring instrument is shown at [0, and the terminal contacts at the connector 24 are shown at 28, 29 and 30, one connected in circuit with each of the wires 2|, 22 and 23 of the triple wire conductor I9. The negative terminal 58 of instrument ID may be connected by a conductor 59 to one end of a calibrating resistance 60, as well known. The opposite end of resistance is connected by a conductor 6| to a contact'terminal 62, for example, of the socket type or of any other type.

The instrument is also provided with a Wheatstone bridge having the fixedresistances 63, 54

and 65, the junctions of the bridge being indicated at 65, 61, 68 and 69. The batteries 3|, 32 are connected in series, as previously explained, with one terminal 34, for example, connected by the conductor 40 to the junction 61. The opposite terminal of batteries 3| and 32 is connected by conductor 22 through battery resistance 'II to terminal contact 29. The junction 69 is. connected by conductor 2| to terminal contact '28, and a terminal contact 12 in proximity to junction 68 is connected by conductor 23 to terminal contact 30. a

The Wheatstone bridge and instrument I0 constitute, in eiiect, a device for measuring resistance for the determination of the thermobulb temperature, the instrument being calibrated in terms of temperature.

For the purpose of recalibrating the instrument '--ence characters -used' -i-n' Figures base I 4" is shown provided w ith openings 120' which the prongs 11, lil and wpfor=example, of 2 the-resistance plugs 'lA,- "l5and' 76- are adapted to contact with contacts 90,9! and-B1.

minal 62, junction-68, and terminali n to -eo-n- 'nect resistance -portion 80 ofthe resistance plug, 'as showndiagrammatically i -in- Figure ,1across terminal-62 and-junction 68, and-resistance por- "tion =8 l of-theresistance plug as -"shown:'

lire--15, across-junctions 8-and terminal 1-2 -In-Figure 7A--the parts -and instrument 7 which correspond to par'ts-"an'd"instrunrentalities Shown in ures 7 and"9 are indicated by primed reference characterscorresponding -to the-meterand- 9l ezr int'o he -inserted and when-'so' inserted :contact'the contact terminals 62, 68andi12.

Although they maybe ofother: resistances for other temperature rangesand :additional r'esisti ance plugs may be provided, in thedrawings' the plug 14 is'for temperatures-from G te-100F11 whereas plug l5 is for temperatures from .1410? .to 200-F., and plug 'ifi is for-temperatures fromr200 to 300 F. The sockets for receiving the'terminal prongs TI, '18 and 'l9 forcontact with-terminal 62, junction"63"andterminal 12: may be "provided, "for example, on therear of base 14, or elsewhere as desired. I

The temperature responsive element or thermoage-raven bulb may be of any suitable or preferred form.

In Figure 9, the thermobulbis shown in the form of a temperature responsive resistance element -85, one end of which is connected by a lead 86 to a terminal contact 81. The opposite end of the temperature responsive resistanceelement 85 is connected by leads 88 and 89 to terminal contacts 90 and 9!. The terminal contacts 28, 29 and30 are adapted for quick detachable conne'cti "f and 'In Figure 2' the-temperature responsiv resistpro. vided at its opposite-end with a terminaliiconnector 95 connected by triple :awires to .lthe tem-- perature responsive element, as previously described. The connection device 96 to which the temperature responsive element is connected by the terminal connector 95 has a terminal connector 91 similar to the terminal connector at one end of the handle Hi.

In order to test the battery voltage to standardize the instrument, the connector shell 25 is applied telescopically over the connector sleeve 43, as shown in dotted lines in Figure 1, the terminal prongs 28, 29 and 30 entering the openings and into contact with terminal contacts 46, 41, and 48. Properly to locate the shell 25 relative to sleeve 43 in applying the shell to the sleeve, the shell has a longitudinally extending channel I00 (Figure 3) which enters only over a small nub or protuberance lDl pressed outwardly from the outer end of the sleeve 43.

Secured internally within the outer wall of channel Hill is a prong I03 (Figure 4) to one side of which nub I0! is adapted to pass in applying shell 25 over sleeve 43. Then after the nub IOI has passed the inner end of prong I03, the shell 25 is turned slightly relative to sleeve 43 to interlock the nub IOI behind the inner end of prong 03, therebyinterlocking the 'shell dli upon the- 'sleeve43. Limited: rotation :of shell 42!. upon sleeve43 is permitted by a circumferentially elongated slot [05 in shell 25, a screwlliB-KFigure 1) being threaded. intothe--sleeve- 43 =with 'its head engagingin slot I 05- to limitirotation of shell 25 on sleeve 43. l v 1 i After thus standardizing the instrument and --with the thermobulb or: temperature responsive resistance element in'position where it:is su-bject'to the temperature which it is desired to measure, the terminal conneoton'Zti, having been disconnected from the sleeve 43, is :applied, 'Lfor example, to the terminal:connector:9 7= in-precisely the same manner in which it is applied to the sleeve 43. This, in effect, places the .terminal contacts 28,:29pand 30 in contact-with the-terminal contacts9039i, and 81 of the. temperature .responsive -resistancezz85, and the temperaturelis vindicated bytthe .po'sitionmofthezpointer 1 l.l.-,relativeiito -the scale I52. of :the instrument.

- lt'InJtesting tor measuringatemperatures .at :a plurality lofrstations or .pointszwithxthe linstrumenttof the present-invention; all "that is required is i to provide atemperature'responsive unitor-thermo- "bulb for each such station or point, -aquick: der ta'chableterminal :connector for each temperature responsive resistancetelement, and a single "portable: resistance thermometer of the character-described foroquick .idetachable connection with the ater-minaL connectors of the respective iz-thermobul-bs or temperature responsive resistance elements."

In. the case of asclosedcompartment crisp ace, such; for example, as arefrigerated car-or:.truck,

the temperature responsive:.resistance aelement I 'may be properly located :within the car, 1 truck I or other space, toaobtain the desired temperature orotherspacefor application oftthe terminal connector 24 of theinstrument theretoirom this way the temperatures at various, stationsor points may be accurately obtainedzwitht a::mini- -mum of fixed installation; also without complicated 'wiring and without selector switch mechanism andwithout separate triplewirecconnections extending from theuindicatorutoeach.of the temperature responsive elements.

The arrangement of the batteries within the handle of the device provides a small, compact, and light weight portable instrument of the order of a flashlight, with the indicator I0 thereon. The arrangement of the standardizing resistance 5| in one end of the handle also makes for compactness and simplicity, and the ability of the terminal connector 24 to be plugged into and out of circuit selectively with either the standardizing resistance 5| or-any of the plurality of temperature responsive resistances or thermobulbs 85 eliminates selector switches and the like, as well as the necessity for switching operations.

It is to be understood that a section of Manganln resistance (not shown) may be provided in the circuit of the instrument for compensation purposes, as known in the art; also that the form of thermobulb may vary widely, and that the terminal connector 24 of the instrument may be connected directly, for example, to a terminal connector on the end of the lead conductor for the thermobulb or temperature responsive resistance element, instead of through a connector device as shown at 96 in Figure 2.

An adjustable magnetic shunt I15 may be provided for adjustment, for example, by a thumb screw H6 for the purpose of adjusting for battery loss, as known in the art.

The embodiment of the invention shown in the drawings is for illustrative purposes only, and it is to be expressly understood that said drawings and the accompanying specification are not to be construed as a definition of the limits or scope of the invention, reference being had to the appended claims for that purpose.

I claim:

1. A portable resistance thermometer comprising, in combination, a tubular handle, an indicating instrument comprising an instrument case mounted on one end of said handle and having a resistance measuring circuit therein, a source of electric energy disposed within said tubular handle and connected in circuit with the resistance measuring circuit, a flexible lead conductor attached at one end to said instrument case and having a plurality of conductor wires leading from the attachment of the lead conductor into the instrument case and connected in circuit with the resistance measuring circuit within the case, a first plug-in connector mounted on the opposite end of said flexible lead conductor for connecting the resistance measuring circuit to an external temperature responsive resistance element, an end cap mounted on the opposite end of said handle, a fixed resistance non-responsive to temperature positioned within said end cap, and a second plug-in connector mounted on said end cap for connection with said first plug-in connector, said second plug-in connector having contacts connected in circuit with said fixed resistance.

2. A portable resistance thermometer according to claim 1 wherein there is a tubular connecting neck between the instrument case and the handle with the circuit connection between the source of electric energy and the resistance measuring circuit extending through said connecting neck.

3. A portable resistance thermometer according to claim 1 wherein the resistance measuring circuit within the instrument case comprises a Wheatstone bridge.

4. A portable resistance thermometer according to claim 1 wherein the resistance measuring circuit within the instrument case comprises a Wheatstone bridge circuit having gaps therein, and a resistance plug having a plug-in connector for connecting resistance portions of said plug across said gaps for adding resistance correlated to the temperature to be measured.

5. A portable resistance thermometer comprising, in combination, a tubular handle, an indicating instrument comprising an instrument case mounted on one end of said handle and having a resistance measuring circuit therein, a source of electric energy disposed within said tubular handle and connected in circuit with the resistance measuring circuit, a flexible lead conductor attached at one end to said instrument case and having a plurality of conductor wires leading from the attachment of the lead conductor into the instrument case and connected in circuit with the resistance measuring circuit within the case, a first plug-in connector mounted on the opposite end of first lead conductor, an end cap mounted on the opposite end of said handle, a fixed resistance non-responsive to temperature positioned within said end cap, a second plug-in connector mounted on said end capfor connection with said first plug-in connector, said second plug-in connector having contacts connected in circuit with said fixed resistance, and an external temperature responsive resistance having a plug-in connector corresponding to said second plug-in connector for connection to said first plug-in connector.

EMIL A. DE BRUYNE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,231,045 Means June 26, 1917 1,323,824 Brueckner Dec. 2, 1919 1,444,771 Baker Feb. 13, 1923 1,978,440 Shepard Oct. 30, 1934 2,016,660 Weeks Oct. 8, 1935 2,098,650v Stein Nov. 9, 1937 2,297,868 Bergeron Oct. 6, 1942 2,457,751 Thompson Dec. 28, 1948 

